Avian hearts have and end-net receptor system present in the myocardium and endocardium but show no evidence of unencapsulated receptors described in the cat. Avian end-net receptor activity, however, displays a similar firing pattern to those receptors in the cat. In addition, these receptors have now been shown to have chemosensitivity to levels of PaCO2 which will effect rate and depth of respiration, as well as, heart rate and stroke volume. The chemosensitive nature of these receptors should be considered equal in its effect to the intrapulmonary chemoreceptors of the avian lung. Characteristics of firing patterns of end-net receptors are to be evaluated with respect to changes in volume and pressure within the left ventricle.